webui : model search functionality in the model selector

It would be useful to have some way to search among the available models in the model selector. Currently, the list can become very long, making it difficult to find what you are looking for:

<img width="400" height="549" alt="Image" src="https://github.com/user-attachments/assets/e064c48b-2958-4e98-8b4a-604d07a826f7" />